"Benign" metastatic meningioma: clinico-pathological analysis of one case metastasising to the lung and overview on the concepts of either primitive or metastatic meningiomas of the lung.

Lung "metastases" of benign meningiomas are rarely described events of biological and clinical interest. We, here, report of a 70-year-old healthy woman found by CT scan to have multiple lesions, the two largest in the right lung on routine examination. Anamnesis revealed that the patient underwent a surgical resection of cerebral meningioma 12 years before. The larger lung lesion was a 3-cm node located in the right lung and was removed by wedge resection. Macroscopically, it showed well-defined borders, whitish colour and firm consistency; histologically, it was uniformly composed by spindle meningothelial cells arranged in fascicules including psammoma bodies. The morphological and immunohistochemical features of this lesion, together with the similarity with the original cerebral tumour and its indolent evolution, led to a final diagnosis of "benign" meningioma metastatic to the lung. Lung metastatic meningiomas may be a diagnostic challenge because of their unusual site of presentation and the possible confusion with primitive lung meningiomas or primary mesenchymal lung lesions. They represent a typical example of "benign" tumours that may implant to the lung similar to other tumours, definitely considered benign but reported to rarely present unusual secondary localization.